A. Field of the Invention
This invention relates to a latch for locking well tools in a well flow conductor. The latch has radially expandable locking keys and also has a valve controlled pressure equalizing fluid passage.
B. The Prior Art
U.S. Pat. No. 3,208,531 to Tamplen issued Sept. 28, 1965 and titled "INSERTING TOOL FOR LOCATING AND ANCHORING A DEVICE IN TUBING" discloses a latch for locking tools in a well flow conductor which has radially expandable locking keys.
The use of an equalizing sub, having a valve controlled pressure equalizing fluid passageway, in conjunction with a latch having radially expandable locking keys, is disclosed on pages 3957 through 3969 of the "COMPOSITE CATALOG OF OIL FIELD EQUIPMENT AND SERVICES", 1974-1975 edition.
These latches and equalizing subs are satisfactory when the well is equipped for service with wire line equipment. However, they could not be used if the well is to be serviced with pumpdown equipment. The length of the disclosed latches is such that the latches are too long to be able to negotiate the bend or curved tubing through which pumpdown equipment must pass. The disclosed equalizing subs simply add length to the latch.
Pumpdown latches have been devised. It has been the practice to position the valved equalizing passage utilized with a pumpdown latch in a separate sub. The sub extends below the latch and is connected thereto by a swivel joint. (See page 4077 of the "COMPOSITE CATALOG OF OIL FIELD EQUIPMENT AND SERVICES" 1974-1975 edition). Such a conventional pumpdown latch and equalizing sub arrangement has several limitations. First, the swivel joint cannot withstand a high pressure differential. Therefore, the pressure range of the latch is limited to the pressure differential that may be withstood by the swivel joint. Second, opening the equalizing passage in the equalizing sub prior to retrieval of the latch is difficult. With the equalizing sub below the latch, a prong must be inserted through the latch bore to move the valve within the equalizing sub. The prong is slightly longer than the length of the latch and is joined to a pumpdown retrieving tool with a swivel joint. To properly align such a prong so that it may pass through the bore of a latch and actuate a valve in an equalizing sub is exceedingly difficult.